After a series of culinary mis-steps (none of which involved sauce), I feel inspired to share some more of the practical wisdom of Marguerite Patten.
Sauce made with a roux (butter and flour) has formed lumps
Whisk the sauce briskly and quite often the lumps will go. If this technique fails then rub the sauce through a sieve or put it into a liquidiser and switch on for a few seconds. This treatment will produce a smooth sauce , but one that becomes thinner in consistency, so allow it to simmer gently for a time so it will become a little thicker.
Sauce too thick
Whisk in extra liquid, but taste the sauce after doing this to make certain there is adequate seasoning and flavouring.
Sauce too thin
Either allow the sauce to cook for a longer period or allow 1 level teaspoon of cornflour to each 150ml (1/4 pint) sauce. You will need to blend the cornflour with 2-3 tablespoons of milk, cream or stock, depending upon the type of sauce. Whisk this into the hot, but not boiling, sauce and stir until thickened. A more subtle method of thickening the sauce [it will hardly know what happened to it] is too blend an egg yolk with a little milk, cream or stock, whisk this into the hot sauce and simmer gently for a short time.
Hot sauce containing egg curdles
Whisk very hard or treat as lumpy sauce above.
Mayonnaise sauce curdles during mixing
Put an egg yolk into a basin and gradually whisk the curdled mayonnaise on to this.
Sauce burns in pan
Do not stir the sauce, pour into a clean saucepan, taste very critically [Should I also frown? Wear a mortarboard?] and you may find the flavour unimpaired. If there is a very slight taste, a little extra flavouring and seasoning (or sugar, in the case of sweet sauce) may disguise this. Put plenty of salt and cold water into the burned pan and leave it to soak.
Scalloped Salmon – tinned salmon, flaked into scallop shell topped with white sauce, breadcrumbs and grated cheddar.
Text and image from The Hostess Book of Entertaining by Marguerite Patten. (Charles and David, 1980.)